Throughout Central Florida, many libraries are lending e-books along with traditional printed volumes. Others plan to do so soon in response to rising demand. Although the boom in sales of electronic reading devices might have signaled trouble for libraries and those endless shelves of bound volumes, it has turned out to be an opportunity.

"This is definitely driven by customer requests," said Tom Merchant, head of library services for Lake County. "Our librarians get asked on an almost daily basis when we are going to start offering e-books, and certainly that's because of the rapid development of e-readers like Kindle, Sony, Nook and so on."

Lake County commissioners signed off this week on a contract between its public library system and a leading national distributor of virtual volumes, called Overdrive. So probably by this fall, anyone with a library card will be able to "check out" a digital copy of the latest bestseller without setting foot in a library.

Orange and Volusia county libraries already have established e-book programs, while others aren't far behind.

In Osceola County, libraries started lending out e-readers at its main branch in Kissimmee to ease users into the technology before e-book access starts this summer. The Winter Park Public Library, which operates separately from the Orange County system, and the Seminole County libraries both plan to join the e-book movement, though neither has a firm start date.

In loaning digital copies, libraries are following the pattern of book sales. The Association of American Publishers reported that e-book sales in February were $90 million, representing growth of 202 percent over the same month in 2010. Meanwhile, sales of printed books have been declining.

Central Florida libraries are reporting similar surges in the circulation of e-books.

Tracy Zampaglione, public-relations administrator for the Orange County Library System, said checkouts of e-books increased from 18,000 in May 2010 to 87,000 in April of this year, in part because the library bought more copies of e-books.

The numbers could spike later this year when Amazon.com adds its popular Kindle to the long list of devices that are compatible with e-book library lending. Borrowing and reading e-books is possible on a slew of products, from laptops to smartphones and tablet computers as well as e-readers — devices created mainly for reading books.

Proponents say e-books are a solution to some of the problems that have always plagued libraries and their patrons, including late returns and fines. The digital version simply disappears from an e-reader at the end of the loan period.

David Burleigh, director of marketing for Overdrive, which hosts the books online for libraries, also notes that libraries can save on staff time and shipping costs involved in handling books.

While e-books can be less expensive than printed copies, there are limits on how widely they can be circulated. Libraries purchase the right to check out a limited number of digital copies of a book at a time. If all the copies have been checked out, readers have to wait for one to become available, just as they do with a printed book.

But do e-books threaten the very idea of libraries as havens for book-lovers or as a civic space for the public?

"It's something we've been worrying about in the library world since the Internet became popular," said Mary Gail Coffee, who works at Winter Park's library.

Coffee said libraries have adapted to the virtual world by embracing it. Most libraries offer free Internet use, and they still draw families through storytelling time for kids or free classes.

Not everything in the library is available in e-book format, so readers may still have to venture into the library for bound volumes as libraries make choices about what e-books they purchase.

E-book enthusiasts praise the savings and convenience that borrowing digitally provides. Lisa Morales, a 49-year-old teacher from Windermere, bought a Barnes & Noble Nook last July. She used to get printed copies of books from Orange County's library system, but now she's all digital. She's even downsizing her small library at home. She's a fan of Florida novelist Carl Hiaasen and mystery writer Harlan Coben, and she can't stand checking out printed copies whose previous borrowers have "dog-eared" the pages.

Morales still loves physical books, but she praises the practicality of e-readers. Last summer, before a family trip, she chose not to fill her backpack with a trove of volumes. Instead, "I put the Nook in my purse, and that's that."